The Rock Swift
I just love these little swifts. We used to call them Blue Bellies, because they have two blue patches on their abdomens. I believe this is a female, they are usually a little lighter in color, and the blue scales on their backs do not stand out as vibrant as they do on the males.
You can easily see, on the tail, where the tail has grown back after an old loss of a tail. The new growth on the tail has none of the blue scales, and the scales are much smaller.